Finely slice the leeks, then tip the leeks into a large bowl and rinse well with cold water.
Add a glug of olive oil to a large frying pan over a medium high heat, add the leeks along with a big pinch of salt and sizzle, stirring often, until softened, around 10-15 mins.
Meanwhile, finely slice the garlic and roughly chop most of the parsley, saving some leaves to serve.
Add the sliced garlic and fennel seeds and cook for a min, then add the butter beans, along with the water from the cans. Add the stock cube and Dijon and bring to the boil. Bubble for 10 mins, until thickened, use a spoon to crush the beans a little to thicken it further.
Add the juice of the lemon and the chopped parsley, season with salt and pepper.
Spoon into bowls and top with a drizzle of yogurt, toasted pumpkin seeds and parsley leaves. Finish with a big crack of black pepper.